PowerMTA Guide
PowerMTA Configuration File Structure
Understand global directives, source blocks, domain blocks and includes.
This guide is designed as a production checklist. Test changes on a staging server and keep a working configuration backup.
Overview
Understand global directives, source blocks, domain blocks and includes. The safest approach is to make one change at a time, validate syntax, reload the service, and then review logs and delivery results.
Configuration example
<virtual-mta vmta1>
smtp-source-host 192.0.2.10 mail1.example.com
</virtual-mta>
<domain hotmail.com>
max-smtp-out 1
max-msg-per-connection 1
retry-after 2h
bounce-after 144h
</domain>Recommended procedure
- Document the current working configuration and relevant IP, DNS and authentication values.
- Confirm that every referenced file, key, hostname and source IP exists.
- Apply the smallest possible change and run the service configuration validator.
- Reload rather than restart when the software supports safe reloads.
- Watch logs, queue growth, SMTP responses and provider-specific behavior.
Common mistakes
- Copying a configuration from a different software release without checking directive support.
- Using a source IP without matching PTR, forward DNS and HELO identity.
- Changing multiple routing and throttling rules at once, making failures difficult to isolate.
- Ignoring envelope sender behavior, bounce handling and complaint suppression.
Verification
systemctl status postfix || systemctl status pmta
ss -lntp
tail -f /var/log/maillog
# Send a controlled test and inspect the complete received headers.Production notes
Delivery settings should be based on current response data, list quality and reputation. A value that works for one server or ISP can be unsafe for another. Prefer conservative defaults and measured increases.